With the universal popularization of the network information industry and the outcoming explosive growth of global data and the rise of the big data industry, data centers have become a new market opportunity of the optical communication industry, and high bandwidth optical interconnection has gradually replaced electrical interconnection, and will develop towards the trend of high speed and large capacity. Multi-channel optical modules adopt multiplex optical emitting and receiving techniques, and have the characteristics of large communication capacity, low energy consumption and miniaturization, which has been favored by the industry. Their transmission rate and transmission capacity are much more superior than single-channel transceiving modules, and have developed rapidly in the recent years, to be one of the main solutions for the developing.
At present, high-speed multi-channel optical modules package multi-channel semiconductor laser/detector array into input/outputted light components with only one light port by wavelength division multiplexing/demultiplexing (wavelength division multiplexing, WDM) technique, as so to improve the transmission speed of the single-end light port. The common packaging forms include CFP, CFP2, CFP4 and QSFP, etc. For example, 4×25 Gbps single mode optical transceiving modules with the packaging form of the QSFP28 module couple four 25 Gbps laser/detector chips with different CWDM wavelengths to a single optical fiber by coarse wavelength division multiplexing/demultiplexing technique, to achieve that a single optical fiber can transmit 100 Gbps signals.
At present, the solutions often used by the wavelength division multiplexing/demultiplexing technique in the industry include: arrayed waveguide grating (AWG) solution, etching grating solution and dielectric thin film filter solution, and so on. The AWG has the advantages of high integration, can be fabricated on one same substrate with the laser chips and detector chips, and has great advantages for multiplexing and demultiplexing applying in more than 4 channels. However, it has high cost, high difficulty in coupling, and big insertion loss, so it is not conducive to meet the requirements on optical transceiving modules for low power consumption. In addition to the defects of its size being a half smaller than that of the AWG and imperfect filtering characteristics, the other advantages and disadvantages of the etching grating solution are similar to those of the AWG. The dielectric thin film filter solution is currently large-scale commercial plan with the advantages of low cost of material and good filtering performance, and the shortcoming is that it is not suitable for the multiplexing/demultiplexing of more channels (more than four channels): as the increasing of the number of the optical channels for multiplexing/demultiplexing, the kinds and amounts of the filters corresponding to the optical channels will increase, the light paths in the optical assembly will be increasingly longer, the requirements on the processing tolerance and the fitting accuracy of the optical elements on the related plane will gradually improve, the difference of the light paths between the optical channels has significant increased, and the insert loss correlative with wavelength has become a problem that has to be solved. At the same time, with the limit of the above fitting accuracy, in the current commercial main solutions of eight channels and above, the light paths of the transmitting component and the receiving component are generally independent, and the transmitting component and the receiving component respectively use a set of filters, so as to significantly increase the number of the independent elements with small size.